Furnaces



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9 ATTORNEYS Jan. 20, 1959 Filed Aug. 50, 1955 B. GREENE FURNACEIS f `7 sheets-sheet '7 .l NVENTOR BEN GREENE- ATTOR NEYS United States Patent@ FURNACES Ben Greene, Berkhamsted, England Application August 30, 1955, Serial No. 531,373

9 Claims. (Cl. 266-5) This invention relates to furnaces of the kind in which articles are heated in a protective or artificial atmosphere, which furnaces are provided with heat insulating nonn metallic refractory linings surrounded by a metal casing. Temperatures up to about 1600 C. may be involved in such furnaces. By protective or artificial atmosphere is meant a non-oxidising, or reducing, or inert atmosphere and includes hydrogen and nitrogen, or argon. The heat retaining capacity of such furnaces is usually very considerable owing to the heat insulating properties of the refractory material and they take a Very considerable period of time to cooldown. ln order to speed up the cooling of the furnace it has already been proposed to provide the furnace with a movable part which exposes a metal wall unprotected by heat insulating material and the present invention is directed to this type of furnace. According to this invention there is provided a furnace comprising separable upper and lower parts, means for imparting relative up and down movement between these parts which upper part is provided with a refractory lining and which lower part comprises an unlined metal wall, a oor for supporting articles to be heated, means for moving the floor in an up and down direction so that in its uppermost position it makesA sealing engagement with the lined upper part and in its lowermost position uncovers saidmetal wall, means for heating the space within said upper part and means for circulating an inert gas through the upper and lower parts of the furnace, and means externally of the furnace for cooling the circulated gas.

The following is a description of a number of alternative forms of furnace according to the invention, reference being made to the accompanying diagrammatic drawings, in which:

Figure l is a vertical section.

Figures 2 to 5 are vertical sections through an alternative form of furnace in which both the hearth and a part associated with the side walls of the furnace are movable in an up and down direction, and which figures show these movable parts during different stages of heating and cooling the articles. f

Figures 6 to 9 are vertical sections through a modified form of furn-ace to that shown in Figures 2 to 5.

Like reference numerals refer to like parts throughout the various figures of the drawing.

In the arrangement shown in Figure 1 the roof 12, side walls 10 and end walls 11 are formed as a unit and comprise refractory material Aarranged within a metal shell 13. Cable and pulley mechanism 16, 17 being pro- `vided to lift the unit which is suspended by the metal eyes 15. In this construction the metal shell is provided with a depending flange 45 which extends into a trough 19 mounted on a supporting frame 46. The hearth 20 is supported on almetal b-ase plate 47 attached to the plunger 48 of a hydraulic ram 49 disposed beneath supporting frame 46. In its uppermost position the hearth 20 abuts the supporting ledges 14 for the refractory walls .of .the furnace. The hearth and the vbase plate may be Patented Jan. 20, 1959 'ice provided with a number of passages 50. The hearth is a comparatively loose fit within the surrounding trough 19, thus when it is lowered any gas displaced by the hearth can readily pass to the upper side thereof maintaining the pressure conditions within the furnace. The side walls are provided with electric heating elements 51, and a draw-off pipe 7 beneath the elements. The vroof is provided with a spy hole 52 and a thermocouple 53. lAn additional supply pipe for hydrogen or other inert gas leads from the supply pipey 24 to a cooler 67 such as a refrigerator which vlatter supplies cooled hydrogen through the pipe 66 and a connection extending through the trough 19 to a point just below the hearth base plate when in a raised position. Although only one pipe is shown preferably a number are provided disposed around the furnaces so as to diffuse the supply of cold hydrogen. .The various pipes for the supply of hydrogen may comprise flexible hose to accommodate the up and down movement of the roof and side walls of the furnace.

When loading the furnace the hearth Ztl is raised to its uppermost position, the unitary walls of the furnace are also raised away from the hearth so that the articles can then be placed on it, whereafter the unit is lowered and protective atmosphere is introduced through the pipe 24 purging the furnace and displacing the air therein. The supply is continued until such time as the iiame may be established at the end of the draw-off pipe 9. The heaters 51 are then energised and the heat treatment of the articles takes place. As soon as the heating is cornplete the hydraulic ram 49 is operated to lower the hearth 20 and thus the interior of the furnace is exposed to the cool walls 19. The supply of hydrogen through the pipe 24 is cut off and the supply of cool hydrogen is estab lished through the pipe 65, refrigerator and pipe 66. The cold hydrogen thus blows on to the previously he-ated material and cools it. Since the draw-off pipe is open, the hot gas is displaced through it rather than being driven through the passages 50 in the hearth and through the outlet 9. When the furnace is sufciently cooled the hearth is again raised Iand the unitary walls of the furnace lifted so that the articles can be removed. Fresh articles are then placed on the hearth and the unitary roof and side Walls lowered. A supply of purging hydrogen is then introduced through the pipe 24 and when purging is complete the heating elements are switched on, both the draw-olf pipes 7 and 9 being open.

in the alternative arrangement shown in Figures 2 to 5 thel hearth 20 is supported by a hydraulic jack 68-on a trolley 54 and is movable towards and away fromthe unitary refractory walls 10, 11 and 12 which may remain in a fixed position. ln this construction there is 'asso ciated with the unitary arrangement of walls 10, V11 and 12 a trough 60 which encircles the walls and into which the aforesaid flangevltl extends. This trough can be raised or lowered in relation to the unitary arrangement of the walls 10, 11 and 12 by hydraulic means not shown andy is itself provided with a iiange 6i. which can dip into a smaller trough 62 formed on the base ,6,3 which carries the hearth 20 and which base is attached to the movable part of the ram. Extending downwardly from this base 63 and around the trolley 54 is a depending wall 64 which may be accommodated in a trough 65 secured to the trolley. Means similar to that described with reference to Figure 9 is provided for raising and lowering the wall independently of the hearth.

The modus operandi is as follows. The work is loaded onto the hearth as shown in Figure 2 and the trolley 54 is then moved into a position beneath the unitary refractory walls iti, 11 and 12 and the trough 60 is lowered so .that the flange 61 dips into the small trough 62 as shown in Figure 4. The inert atmosphere is then introduced .through the pipes Sand 24 purging the-fur-t heating is being carried out.

nace-.andpassing vout of the pipe. 9.n YWhen the furnace is purged the trough 60 is l.again elevated as is also the hearth as shown in Figure 3, and the heating elements are energised.` The inert atmosphereis then cut olf Vfrom the pipe 24 but may be established through the pipe 8, thus a comparatively cool volume of gas is disposed beneath the hearth. When the articles have been sufficiently heated the trough 60 and hearth 20 `are again lowered as shown in Figure 4 and the supply of hydrogen through the pipe 8 is established if not already on and blows to the articles and cools them and passes out through the pipe 9 then above the hearth. Instead of passing to the atmosphere the hydrogen is circulated through a cooler back to the pipe 8f Finally, when the articles are suciently cooled the trough 6tl is again elevated and then the trolley can be moved away as shown in Figure 5, and the articles removed.

The construction shown in Figures 6 to 9 differs from the construction shown in Figures 2 to 5 mainly in that the trough 60 and depending flange 61 is dispensed with and the ange 18 is movable into and out of the trough 62 and the height of the other troughs are reduced. The hydraulic jack 68 is provided with heat protecting bellows 69 which at its upper end may be secured to the lower part of the hearth 20 while its lower end is connected to the inner wall of the trough 65 which is mounted directly on the trolley 54. The wall 64 may be raised and lowered independently of the hearth 20 by mechanism best seen in Figure 9. This comprises a lever arm 76 txed to a cros's shaft 71 mounted in bear ings carried by brackets 72 secured to the trolley 54. The cross shaft also has secured to it two arms 73 which straddle the trough 65 and are provided at their extremities withrollers 76. The rollers are arranged to engage the underfaces of abutments 77 extending downwardly from a shoulder provided between the main portion of the wall 64 and a reduced lower portion 78. In order to retain` the wall 64 in the uppermost position the lever arm 70 and the bracket 72 may be provided with holes 79 and 80 and a locking pin is passed through these holes when they are in register. The disposition of the parts shown in Figure 6 is similar to that shown in Figure 3 andwhich is the position they assume when In Figure 7 the parts are shown in the position assumed when cooling is being carried out and in this case the hearth 20 has been lowered. As in the construction shown in Figure 1 an additional supply pipe (not shown but similar to 66 of Figure 1) is provided for supplying cooled hydrogen to the lower part of the furnace. Figure 8 shows the position of the parts similar to those shown in Figures 2 and 5, where the wall 64 has been lowered thereby retracting the trough 60 from the flange 18 thereby enabling the hearth to be wheeled away from the upper part of the furnace whereafter the hearth 20 may be raised by the jack for removing the cooled articles. The

walls 64 may be provided with suitable cooling tins 79.

I claim:

l. A furnace comprising separable upper and lowerv parts, means for imparting relative up and down movement between these parts which upper part is provided with a refractory lining and which lower part comprises an unlined metal wall, a Hoor for supporting articles to be heated, means for moving the oor in an up and down direction so that in its uppermost position it makes sealing engagement with the lined upper part and in its lowermost position uncovers said metal wall, means for heating the space within said upper part, means for circulating an inert gas through the upper and lower parts `of the furnace and means externally of the furnace for cooling the circulated gas.

2. A furnace according to claim l wherein said means for circulating the inert gas through the furnace comprise inlet and outlet pipes communicating respectively d with therelatively movable upper and lower parts of the furnace. u

3. A furnace according to claim 1 wherein the means for circulating the inert gas through the furnace and cooling means comprise an inlet pipe communicating with the upper end of the upper part of the furnace and an inlet pipe communicating with the lower part at a location which is below said oor when in its uppermost position.

4. A furnace according to claim 1 wherein the oor is provided with passages extending through the thickness thereof.

5. A furnace according to claim 1 wherein the upper part of the furnace is provided with a refractory lining and wherein a oor for supporting the articles to be heated is movable in an up and down direction and is also provided with a refractory lining which makes sealing engagement with the lining of the upper part of the furnace which floor is provided with passages extending through the thickness thereof and wherein the means for circulating the inert gas through the furnace and cooling means comprise an inlet pipe communicatingwith the upper end of the upper part of the furnace and an inlet pipe communicating with the lower part at a location which is below said floor when in its uppermost position.

6. A furnace according to claim l wherein said upper part of the furnace comprises a steel casing lined with refractory material and the lower part comprises an unlined metal casing and wherein a floor for supporting the articles to be heated is movable in an up and down direc tion from a position in which it is at the lower end of the unlined casing to a position in which it makes a sealing engagement with the lining of the upper part of the furnace and wherein the meansfor circulating the inert gas through the furnace ,and cooling means cornprise an inlet pipe communicating with the upper end of the upper part of the furnace and an inlet pipe communicating with the lower part at a location which is below said floor when in its uppermost position.

7. A furnace according to claim 1 wherein said upper part of the furnace comprises a steel casing lined with refractory material and the lower part comprises spaced metal walls of a cooling jacket and wherein a floor for supporting the articles to be heated is movable in an up and down direction from a position in which it is at the lower end of the cooling jacket to a position in which it makes a sealing engagement with the lining of the upper part of the furnace and wherein the means for circulating the inert gas through the furnace and coolingl means comprise an inlet pipe extending through the lining at the upper end of the upper part of the furnace and an outlet pipe extending through the two walls of the jacket at a location which is below the oor when the latter is in sealing engagement with said lining.

8. A furnace according to claim 1 wherein said lower part is lixed and means are provided for moving the upper part in an up and down direction from a position in which it makes sealing engagement with the lower part to a position leaving a gap between these parts through which articles to be treated may be introduced and withdrawn; which upper part is lined with refractorymaterial and the lower part is unlined, and wherein a oor for supporting articles to be treated is movable in ran..up and down direction relatively to the xed lower part so that in its uppermost position it makes sealing engagement with the lined upper part when in its lower position.

9. A furnace according'to claim 1 wherein said lower part is xed and means are provided for moving the upper part in an up and down direction from a position in which it makes sealing engagement with the lower part to a position leaving a gap between these parts through which articles to he treated may be introduced and withdrawn; which upper part is lined with refractory material and the lower part is unlined, and wherein a oor for supporting articles to be treated is movable in an up and down direction relatively to the fixed lower part so that in its uppermost position it makes sealing engagement with the lined upper part when in its lower position and wherein means for circulating the inert gas through the furnace and cooling means comprise an inlet pipe communicating with the upper end of the upper part of the furnace and an inlet pipe communicating with the lower part at a location which is below said oor when in its uppermost position.

References Cited in the le of this patent Cope Dec. 11, 1928 6 Schonbrunn et al. Ian. 1, 1929 Fuchs Ian. 22, 1929 Von Forster et al Dec. 22, 1931 Seastone July 26, 1932 Kenworthy Sept. 13, 1932 Owen May 15, 1934 Arkema Mar. 19, 1935 Erberwein June 1, 1937 Roth Jan. 7, 1941 Germany Aug. 2, 1942 FOREIGN PATENTS Italy Jan. 28, 1930 Italy May 12, 1934 

